Aging damage, deformation characteristic and mechanical properties analysis of Inconel 625 based on small punch test

Inconel 625, valued for its excellent overall performance, is widely used as a key component material in pressurised water reactors. With increasing service time, notable changes occur in both the microstructure and macroscopic deformation behaviour of Inconel 625. In this study, small punch tests were performed to evaluate aging damage, deformation characteristics and mechanical properties of Inconel 625. As the aging time increases, the small punch curves shift to the lower left along with the increase in tensile strength and the decrease in elongation. A large amount of needle-shaped δ phase are observed during long-term aging. The dynamic strain aging (DSA) characteristic gradually becomes progressively less evident as the aging time increases. Meanwhile, it has been shown that the variation trend in serration type with different deformation rates is not affected by aging damage. Based on slope analysis, the minimum slope point in the elastic–plastic stage and the inflection point in the membrane stretching stage were examined. Yield and ultimate tensile strength estimation methods were developed based on deformation energy and inflection-point parameters. The results demonstrate that the small punch technique is an effective approach for characterising the deformation behaviour of aged materials and can serve as a reliable reference for mechanical-property evaluation.